Neuroblastoma remains one of the deadliest cancers in children and we are reaching a plateau in our ability to improve survival with increasing intensity of therapy. Thus, future treatment strategies must rationally exploit known tumor specific alterations. Despite thirty years of knowledge of recurrent genomic abnormalities in neuroblastoma, other than the neuroblastoma oncogene MYCN, the gene targets of these aberrations has remained unknown, and no bona-fide neuroblastoma tumor suppressor genes have been identified. The discovery of a new class of regulatory non coding RNAs called microRNAs (miRNAs) are attractive candidate neuroblastoma oncogenes and tumor suppressor genes because of their role in normal embryonic development and in cancer. We hypothesize that oncogenic and tumor suppressor microRNAs (oncomirs) contribute to neuroblastoma tumorigenesis. This proposal seeks to test this by 1) Identifying neuroblastoma oncomirs through an integrative genomic approach, 2) Characterizing the tumor suppressor mechanism of the miR-34 family (and other identified oncomirs) in neuroblastoma and 3) Demonstrating preclinical therapeutic efficacy of miR-34a replacement in vivo. The discoveries made from this work will have broader application to cancer biology as many of the genomic alterations found in neuroblastoma are also found in other pediatric and adult solid tumors. This proposal lays out a 5-year research and training program with the ultimate goal to transition the principal investigator to an independent R01-funded physician-scientist. Her mentors and advisors are leaders in the field of neuroblastoma, translational genomics and gene therapy. She will take advantage of the ample resources of her environment, both at the Children's Hospital of Philadelphia and at the University of Pennsylvania. RELEVANCE (See instructions): Most children with neuroblastoma have high risk disease and survival rates for these patients' remains less than 40%, despite intensification of cytotoxic therapy. Advances in cure rates will result from radically new treatment strategies based on the fundamental alterations present in the malignant neuroblast. We propose to identify oncogenic and tumor suppressor miRNAs through an integrative genomics approach and to further characterize them for translation into novel therapies for children with high risk neuroblastoma.